Machine tool utilizing a potentiometer for determining various positions

ABSTRACT

Machine tool in which movement of the table over the base is produced by a torque-controlled motor and in which the table positions are determined by means of a potentiometer and of preset resistance. At a pre-determined position, a stop element on the base engages a stop element on the table. During the engagement of these stop elements, the torque generated by the motor remains at a preselected value.

United States Patent [191 Wake et al. Dec. 24, 1974 MACHINE TOOLUTILIZING A 3.254,2s3 5/1966 Hunt 318/663 O N IO O DETERMINING3,467,900v 9/1969 Benton 318/663 X 2 2221;; 21:22; 111;: 1121:42 2 [75]Inventors: John A. Wake, Auburn; Arthur F. y I j IIIIIIIIIIIIIIIII I hSt. Andre, lVlarlboro, both of Mass. Primary Examiner B Dobeck [73]Ass1gnee: gancmnati hfilacron-Heald Corp., Attorney, Agent,'orFirmNorman S. Blodgett; Gerry orcester, ass. A. Blodgett [22] Filed:Mar. 9, 1973 [21] Appl. No.: 339,705 57 ABSTRACT Machine tool in whichmovement of the table over the [52] Cl 318/663 22 4 47 base is producedby a torque-controlled motor and in Int Cl Gosb 1/06 which the tablepositions are determined by means of 58 Field of Search 318/663, 665,571, 436, 3 l resstanceh a 318/467 626 etermme posltlon, a stop e ementon t e base engages a stop element on the table. During the engage-References Cited ment of these stop elements, the torque generated byUNITED STATES PATENTS the motor remains at a preselected value.

3,013,195 12/1961 Langham .Q 318/663 X 8 Claims, 18 Drawing FiguresPATENTED 3.857, 079 sum 01 0H6 PATENTEU SHEU DEUF l6 PATENT nuEcwsM 30 m079 SHEET w 0F x SECOND TABLE FIRST TABLE BORINGHD START v 195391? D Y DN a Y I M CENTER mp HE C522?- BACK BORE. SECOND TABLE. FIRST TABLEBDRINGHID 5mm TERWOP M J4 VH4 BACK BORE 5ECOND FLED FIRST FEEDBORINGHEAD RAPID RAVERSE urn; AT; wan. man;

' MASTER START PUSH BUTTON PAIEIII'EU 3.857, 079

SHEET 050T I6 CYCLE DIAGRAM {MASTER CONTROL RELAY 26CR X SLIDE REAR||4CR II9CR IIZICENTER STOP KNOB 57 TABLE LEFT KNOB 55 SWITCH 5 PusHBUTTON 52 POT I NOB 56 POT 3L LS 2 T* QE'$ SQ POT 2L sECoND TABLE Pos.

{ FIRST liAgIE P0s. F2 I CR W 'l LIL-R11 POT I FEED 2 POT(KNOB 6|) I IFEED IP0T(KN0B e2) LoAD I POT I SOL-4 2 I CURRENT LIMIT IFEED T IgcITABLE LEFT AT R.T. L.I-I-R.T. PoT 2k I KNOB 46 I 2 I POT 4L SOL!)f I R.sToP W I ma POT 5L IE I POT 5L CURRENT LIMIT I+ l4 CR I IZCRPIE I 2ICRFEED 2 POTPIG I R.H.- RT. POT n TABLE RIGHT AT RT. L.H.-R.T. POT

- I I I I POT IL 5 POT 2Lg E POT 3L- k- PDT ILaIe LS Z-Ik I I R I I:BCRk ITTR* POT IR POT 3R I RHBoRINGHEAD POT 2R w L.S.3

sTART POS. FIRST TABLE POS. l7 CR TABLE Is RIGHT I ISCR IIGCR QCR M3 IFEED I POT FEED 2 POT I I I soL 5 TABLE RIGHTATRI; R R.H.-R.T. POTI POT4 R l9 TR BACKBORE POS:

I CURRENT LIMIT I FEED I POT I I I 1 4 BORE R.H.CTR. STOP POT 5R 9K 5FACE :IQCRaK I zIcRaIe TcR I L.H.-R.T. POT k 6CR 2% POT 5R ITCR |I9 CRFEED 2 POT -)k I 2| CR IBCR eIE 7 CRaK CURRENT LIMITIP LOAD L HYPER LooeIe TABLE LEFT AT RT. POT 6 I l POT IR-gg- POT ZRlk POT 3Rak POT4Re|ePATH-JEW 2 41974 SHEET 070E K6 SHEETI LINE 20] LINE 203 T FB +LINE 206LINE 205 I a, k TABLE LEFT L. ,98 LIMIT SWITCH CLOSES WITH TABLE AT L.H.POS. STOP TABLE IS LEFT L82 85 I0 SE TIMER TABLE LIMIT SWITCH CLOSESWITH IMEG 7T T TABLE AT RH. PO S.STOP TIMER Jo h m TABLE Is IIO SEC.TIMER R'GHT TABLE 99 0 9T RIGHT A 49 57 I LEFT HAND I @I fifi BORING I lIOCR /V\ Q EQQ I (a/XI P05. 56 I l FEE POTZ I P08.

'{E)@. some I I LEFT I I 55 I I 47 SECOND I I I TABLE 1 lzcR Ne 6) ILEFT 54 I LEFT %E I I w HAND I 6CR 20R BACKBORE (:::)(::)+o{l 1I L I'POS. 58 l CENTER I I G STOP E? V P08.

{B}: 3 MGR LEFT HAND PATENTED M N 37857 079 sum lBOF 16 AMPLIFIED DRIVENPOT SIGNAL INPUT +24V POTI 4 INPUT P 2 E 6 No.2 INP UT T OUTPUT POT3 2I@N0.3 INPUT I OUTPUT P0T4 l I NO.4 INPUT OUTPUT POTS |O 3 No.5 INPUTOUTPUT LL. LL

E E FIG.|8

I- I- r 9 2| 5 ICIB -I5V-l5V COMM. com M.

II Q AMPLIFIED SHIFT DRIVEN PoT SIGNAL BACKGROUND OF THE INVENTION Inthe design of a machine tool the regulation of the traverse motion,i.e., the motion of the tool in and out of the work in its axialdirection, is very important. Not only is the rate of traverse feedimportant, but also the point at which transition from one feed rate toanother takes place is also very important. This is important in orderto obtain accuracy of work and quality of finish on the finishedsurface. In the past, the motion of amachine tool table has been broughtabout mostly by use of a hydraulic cylinder. The transition points andthe rate of feed has been regulated by the use of valves. Since thesevalves represent the restriction of flow of hydraulic fluid underpressure, they generate considerable heat and this heat is carriedthroughout the entire hydraulic system, including the large traversecylinder which lies deep within the body of the machine tool.

The result is that, as the temperature of the working fluid changesduring the working day, the thermal expansion and contraction of themachine tool structure introduces errors. In addition, although the useof hydraulic actuation is tempting because of its initial simplicity,the hydraulic system. becomesvery intricate when the machine tooltraverse-motion cycle becomes complex. This means that the machine toolbecomes covered with hydraulic lines and large hydraulic valves andsolenoids. Furthermore, the hydraulic system is slow in response tocontrol signals and, therefore, introduces substantial control lag intothe system. These and other difficulties experienced with the prior artdevices have been obviated in a novel manner by the present invention.

It is, therefore, an outstanding object of the invention to provide amachine tool whose traverse motion is brought about entirely by the useof an electrical actuator and electrical controls. 1

Another object of this invention is the provision of a machine toolwhich is free of hydraulic lines and valves.

4 A further object ofthe present invention is the provision of a machinetool in which the traverse motion takes place substantially without thegeneration of heat, so that the thermal expansion and contraction of themachine tool elements is reduced to a minimum.

It is another object of the instant invention to provide a machine toolin which a substantial portion of the controls are in the forms oftransitorized intergrated circuit logic controls, so that the controlsare not only rugged, but take up little space and are easily replaceableon a unit basis.

With these and other objects in view, as will be apparent to thoseskilled in the art, the invention resides in the combination of partsset forth in the specification and covered by the claims appendedhereto.

SUMMARY OF THE INVENTION I eter. A stop element on the base engages astop ele ment on the table at a point in the sliding movement. A switchis mounted in front of one of the stop elements and is actuated by theother stop element. The torque generated by the actuator remains at apre selected value during contact between the stop elements.

BRIEF DESCRIPTION OF THE DRAWINGS The character of the invention,however, may be best understood by reference to one of its structuralforms, as illustrated by the accompanying drawings, in which:

FIG. 1 is a perspective view of a machine tool embodying the principlesof the present invention,

FIG. 2 is a perspective view of a portion of the machine with upperelemen'ts removed to show the details of an actuator,

FIG. 3 is an exploded view of the actuator,

FIG. 4 is a front elevational view of a control panel.

FIG. 5 is a sectional view taken on the line VV of FIG. 2,

'FIG. 6 is a cycle diagram showing the operation of the machine,

FIG. 7 is a detailed cycle diagram showing the operation of the machineand the elements which take part in the various parts of the cycle,

FIG. 8 is a sectional view taken on the line VIIIVIII of FIG. 2,

FIG. 9 is a sectional view taken on the line IX-IX of FIG. 8,

FIGS. 10-16 are electrical schematic diagrams showing the electricalequipment used in the machine tool, and

FIGS. 17 and 18 are electrical schematic diagrams of printed circuitboards used in the control of the machine tool.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring first to FIG. 1,wherein are best shown the general features of the invention, themachine tool, indicated generally by the reference number 10, is shownas being in the form ofa double-ended boring machine, having a base 11,on which a table 12 is mounted for sliding movement. An actuator 13,including a motor 14, is operative between the base and the table. Thetorque and speed of the motor 14 is controllable by apparatus located ina control cabinet 15. A control cabinet 16 contains the boring headspeed control. Located at the front of the base 11 are control panels 17and 18, which are substantially the same, but are at opposite I ends ofthe base for the convenience of the operator.

Mounted on the base 1], overlying the table 12 at the end of the baseadjacent the control panel I7 is a bridge 19 on which is mounted atoolhead 21. At the other end of the base is a bridge 22 adapted tocarry another toolhead 23. The toolheads 21 and 23 are of theconventional type used in boring machines and include, not only a toolspindle, but the motor for driving the spindle. Mounted on the table 12between the bridges I9 and 22, is a workholder 24. Extending upwardlyfrom the base 11 is a stop element 25 which is adapted to be engaged bya similar stop element extending downwardly from the table 12 (see FIG.9).

Referring now to FIG. 2, it can be seen that the actuator I3 and itsmotor 14 are mounted in a casting 26, which in turn is bolted to thebase 11 which also carries the stop element 25. The actuator 13 includesa ball screw mechanism, including a screw 27 which is driven by themotor 14 and a nut 28 which is mounted on an abutment 29 is bolted tothe underside of the table 12. Suitable ways 31 and 32 are carried bythe base 11 to support and guide the table 12 in its sliding movementrelative to the base. A casting 26 is formed with a box 33 adapted tocarry a potentiometer-driving mechanism (which will be described infurther detail hereinafter) and has attached to it a cover 34 having abox-like configuration for enveloping a primary potentiometer. Mountedat the rear of the base 11 are lubrication apparatus 35 of the usualtype for supplying the various elements including the ways 31 and 32with suitable lubrication.

In FIG. 3 can be seen some of the details of the actuator 13. A coupling36 is mounted on the screw 27 and drives the screw using motor 14 asmotive power. It carries a sprocket gear 37 connected through a clutchby a sprocket chain 38 which drives a sprocket gear 39 mounted on ashaft of a gear reduction unit 41. The

output of the unit 41 is connected through a clutch to the shaft 42 of aprimary potentiometer 43. This potentiometer has its resistance elementin the form of a helix. The shaft 42 is provided with a screw elementwhich carries the actuator along the helix. It is possible with thisconstruction to obtain an extremely long potentiometer resistanceelement in a small space. The bellows 44 is provided to extend betweenthe casting 33 on one end and the abutment 29 on the other hand toprotect the portion of the screw 27 extending between these elements.Furthermore, a rigid cover 45 is provided to extend from the other sideof the abutment 29 to also protect the free end of the screw 27.

The control panel 17, shown in FIG. 4, indicates most of the controlsthat are used in the operation of the machine. Along the top roware fiveindicator lamps which become lighted at various times. These include aBACK BORE POSITION lamp 46, a SECOND TABLE POSITION lamp 47, a FIRSTTABLE POSITION lamp 48, a BORING HEAD START POSITION lamp 49 and aCENTER STOP POSITION lamp 50. In the same top row are located a TABLELEFT manual switch 52 and a TABLE RIGHT manual switch 53. The second rowincludes 5 knobs which are used for setting secondary potentiometers,these include a BACK BORE POSI- TION knob 54, a SECOND TABLE POSITIONknob 55, a FIRST TABLE POSITION knob 56, a BORING HEAD START POSITIONknob 57, and a CENTER STOP POSITION knob 58. Each of these knobs is ofthe type which includes, not only a setable potentiometer, but theturning of the knob to set the potentiometer causes a setting of avisual readout on the face of the knob. The face of the knob thuscarries a designation of the exact position of the contactor of thepotentiometer in along its resistor in terms of a three-place decimaldesignation of the percentage of the length of the potentiometerresistor on which the contactor is positioned.

The third row contains 5 knobs for controlling speed and rate. Theyinclude a BACK BORE RATE knob 59, a SECOND FEED RATE knob 61, 21 FIRSTFEED RATE knob 62, a BORING HEAD SPEED knob 63, and a RAPID TRAVERSERATE knob 64. Basically, these knobs include a variable resistor whichcan be adjusted by the rotation of the knob and they include a visualindication on the face of the knob of the decimal portion of theresistor which is effective. At the bottom right-hand corner of thepanel are located various elements, including a CONTROL ON lamp 65, aHEAD SWITCH 66, which is shiftable from a hand position to an autoposition, a MASTER START switch 67, :1 HEAD .IOG switch 68, a MASTERSTOP switch 69, and a TABLE STOP switch 71.

In FIG. 5 are shown the details of the equipment associated with theprimary potentiometer 43 and the contactor shaft 42. The potentiometeris connected by a coupling 72 to the output shaft of the reduction unit41. Within the envelope provided by the cover 34 is a support 73 whichis used for making the electrical connections from the main controls tothe primary potentiometer 43.

FIGS. 8 and 9 show the details of the manner in which the switchassociated with the stop element 25 operates. It consists of a plunger74 which is slidably carried in a bore 75 formed in the casting 26extending upwardly from the base 11. The bore 75 is provided with acounterbore 76 in which resides an enlarged portion 77 of the plunger. Acontact rod 78 extends through the plunger and is adjustably positionedrelatively thereto because of the fact that it is threaded and providedwith nuts 79 and 80. The coil spring 81 biases the plunger to the rightin the bore 75, while the shoulder between the counterbore 76 and themain part of the bore 75, limits its motion in the other direction whenbrought into contact with the table 12. When it moves to the left in thecounterbore 76, the enlarged portion 77 of the plunger engages aslidable pin 82, this engages one end of a lever 83 which is hindgedlymounted on a vertical pivot pin 84. The other end of the lever engages amicro-switch 85. The coil spring 86 biases the lever toward themicro-switch.

FIG. 9 shows the manner in which the table 12 engages the stop element25. The table 12 is provided with a downwardly-depending abutment 87having a vertical surface provided with a hardened metal button 88. Thebutton is lined up with the rod 78 for engagement therewith.

FIG. 6 describes, in general, the manner in which a cycle of the machineoperates. At the point 1, the table 12 is in a central position with theworkholder 24 located midway between the toolheads 21 and 23. The tablemoves to the left on a rapid traverse to the point 2. At the point 2 theworkpiece is engaged by the tool and the operation proceeds from thepoint 2 to the point 3. At thepoint 3, the table is traversed to theright, passes completely through the central position and continues tothe point 4 where the workpiece and the tool in the toolhead 23 areengaged. The machining operation with the toolhead 23 continues frompoint 4 to the point 5 at which time the'table is turned to the left andstops in the central position at the point 6. Electrical apparatus thatis necessary for performing this movement is shown in FIGS. 10-16.

FIG. 10 shows the three phase lines 89, and 91 entering the system andsupplying the power to a lefthand boring-head motor M and a right-handboringhead motor M These lines are also connected to suitable portionsof the motor-control unit 92. This motorcontrol unit is a servo-drivesystem manufactured by Hyper-loop Inc. of Bridgeview, Ill., anddesignated as their HLS ldJ/IW. It serves to control the torque andspeed generated by the motor 14. Two of the lines 89 and 90 areconnected to the primary of a transformer 93 whose secondary suppliesthe power lines 94 and 95 which is used with the remainder of theelectrical control. Of particular interest in this portion of theelectrical schematic is the left-hand brake actuating solenoid SOL 4,and the right-hand brake actuating solenoid SOL 5.

In FIG. 11, it can be seen that the l l5-volt AC power lines 94 and 95are connected to the input of a power supply 96, having a 24-volt DCoutput which are connected to lines 97 and 98. Of interest in thisportion of the controls is the left-hand limit switch LS2 and theright-hand limit switch LS3, (since the right-hand end of the base isprovided with a stop element similar to the stop element 25 and with asimilar limit switch LS3).

In FIG. 12, it can be seen that the elements are connected to twocircuit boards 99 and 100. Circuit board 99 is shown in FIG. 15, whilethe circuit board 100 is shown in FIG. 16. FIG. 12 also shows the way inwhich the lamps 46 through 50. are incorporated into the circuitry. Italso shows the way in which the potentiometer is associated with theknobs 54 through 58 are incorporated into the circuitry. The primarypotentiometer 43, is also shown in the circuitry.

It should be noted that some of the elements in the electrical controlshave to do with a cross-slide arrangement built into the workholder 24and incorporating the same type of ball-screw drive and torquecontrolledmotor as is used for the main traverse. No

attempt is made to describe its operation in connection with the presentinvention, but the circuit board 101 in FIG. 13 is associated with thecontrol of this motion. Also, the motor control unit 92 appears in thisview and is connected in a suitable manner.

In FIG. 14, it can be seen that the elements are also connected to themotor control unit 92 and connected into the circuitry are thepotentiometers associated with the knobs 59, 61, 62 and 64.

FIG. 15 shows the circuit board 99. It shows that it consists of anumber of operational amplifiers associated with transistors and with aDC-to-DC convertor 102.

Similarly, FIG. 16 shows the details of the circuit board 100. Thecircuit board 101 is exactly the same, but, of course, connected in adifferent way to different parts of the circuit. Generally speaking, theboard 100 consists of a number of operational amplifier units connectedto transistors. The boards 99, 100 and 101 are printed circuit boardswhich reside in the control cabinets 15 and I6 and which, in accordancewith common practice, may be readily replaced by a sliding action. Theyare printed circuits combined with logic circuits and transistors togive a compact rugged construction.

The operation of the apparatus will now be readily understood in view ofthe above description and particularly in conjunction with anexamination of FIG. 7. With the motors operating in the toolheads 21 and23 and'the actuator motor 14 energized, as well as the motor controlunit 92, the table is set in motion to the left by actuating the TABLELEFT push button 52. The knob 57 determines the point at which thelefthand boring head is started. When it has started, the lamp 49 lightsup. The table reaches the first position, as determined by the FIRSTPOSITION knob 56. The FIRST POSITION lamp 48 lights up. The boringoperation starts with the boring head speed as set by the knob 63 and isfed axially at the rate determined by the knob 62. Eventually, the tablereaches the point determined by the SECOND TABLE POSITION knob 55 andthe SECOND TABLE POSITION lamp 47 lights up. The second boring operationstarts up at a second feed rate determined by the knob 61. Incidentally,the rapid traverse rate, as the table moves from point I to point 2, isdetermined by the setting of the resistor associated with the RAPIDTRAVERSE RATE knob 64, and of course, the boring head speed isdetermined by the knob 63. In FIG. 7, also it should be noted that, theasterisk appearing in various places indicate that the element concernedhas been dropped out at that particular point.

As the table approaches the left-hand side, and the button 88 on theabutment 87 of the table 12, engages the stop rod 78, the plunger 74 ispushed to the left against the spring pressure of the coil spring 81.Eventually, the shoulder between the enlarged portion 77 and the rest ofthe plunger 74, engages the end of the pin 82 and the pin, in turn,pushes the lever 83 rotating it in a clockwise direction (as viewed inFIG. 8). This clockwise direction is contrary to the spring biasintroduced to it by the spring 86 and serves to actuate the spring 85.As a matter of fact, it closes the microswitch 85, which starts a timer;after'the preselected time has passed, the timer acts to reverse themotion of the table by reversing the direction of rotation of the motor.The motor-control unit 92 has been actuated by the FIRST TABLE POSITIONpotentiometer 48 in such a way that the torque in the motor l4 islimited. This means that the motor operating through the screw 27 andthe nut 28 produces a force by which the table 12 engages the stopelement 25 and pushes against it. A plunger 74 has been pushed to theleft (in FIG. 8) in amounts sufficient for the shoulder on the enlargedportion 77 to engage the bottom of the counterbore 76 so that it can gono further and so that further action operates through the casting 26into the base II. In other words, the table 12 pushes against a stop onthe base 11 with a force determined by the limited torque in the motor14. It remains in this position for a time as determined by the time 103in FIG. 11. This means that the boring tool operates to clean up ashoulder for a length of time determined by the timer and thisparticular shoulder is cleaned up while the table is pressed to the leftagainst a stop with a predetermined force. This gives exactrepeatability of the position of the finished surface thus produced. Itshould be noted that a tachometer 104 is attached to the outboard end ofthe motor 14 as indicated in FIGS. 3 and It).

It is obvious that minor changes may be made in the form andconstruction of the invention without departing from the material spiritthereof. It is not, however, desired to confine. the invention to theexact form herein shown and described, but it is desired to include allsuch as properly come within the scope claimed.

The invention having been thus described, what is claimed as new anddesired to secure by Letters Patent is:

I. A machine tool, comprising a. a base,

b. a table mounted for sliding movement on the base,

c. an actuator operative between the base and the table, the torque andspeed of the actuator being controllable,

cl. a primary potentiometer connected to the actuator,

1. A machine tool, comprising a. a base, b. a table mounted for slidingmovement on the base, c. an actuator operative between the base and thetable, the torque and speed of the actuator being controllable, d. aprimary potentiometer connected to the actuator, e. a plurality ofsecondary potentiometers set at selected values, f. a control forcomparing signals from the secondary potentiometers with a signal fromthe primary potentiometers, and g. a stop element on the base engaging astop element on the table at a point in the sliding movement, and h.means causing the torque generated by the actuator to remain at apre-selected value during engagement between the stop elements.
 2. Amachine tool as recited in claim 1, wherein the actuator is a ball-screwmechanism rotated by a torque-controlled motor.
 3. A machine tool asrecited in claim 1, wherein the primary potentiometer includes a helicalresistance element and a contactor driven by the actuator.
 4. A machinetool as recited in claim 1, wherein the secondary potentiometers areindividually adjustable to give voltage settings corresponding tovarious locations in the sliding movement between the table and thebase.
 5. A machine tool as recited in claim 1, wherein one of the stopelements has a switch mounted for actuation by the other stop element,and wherein the switch is located so that it is actuated slightly beforepositive engagement takes place between the stop elements.
 6. A machinetool as recited in claim 1, wherein a digital display mounted on thebase gives a continuous indication of the condition of the primarypotentiometer and, therefore, of the position of the table relative tothe base.
 7. A machine tool as recited in claim 6, wherein the secondarypotentiometers are individually adjustable and each carries a displaywhich is indicative of the value of the setting at all times.
 8. Amachine tool as recited in claim 7, wherein a coincidence of the valueof the primary potentiometer with the setting on a secondarypotentiometer serves to set in motion a change of mode of operation ofthe actuator.